The present invention relates to a robot apparatus for transmitting a signal for a robot hand between a robot hand and an external robot controller to drive the hand and, more particularly, to a robot apparatus which can identify a state wherein the robot hand is separated from an arm, and a state wherein a failure occurs on a transmission path.
In general, when one robot is caused to perform various jobs, hands must be exchanged depending on jobs. For this reason, the distal end of an arm of the robot must have a hand attaching/detaching device for attaching/detaching the hands. The hand attaching/detaching device also requires a structure having a connection mechanism for supplying air and power to the hand, and for performing communication, and the like.
As a conventional hand attaching/detaching device as described above, Japanese Patent Laid-Open No. 58-186589 is known. In this reference, in order to reduce a shape in a Z-axis direction (a direction to disengage a hand), a locking ball is supported on a hand attaching/detaching device connected to a robot arm via an outward tapered surface so as to be reciprocal in a radial direction, and an inward tapered surface engaging with the locking ball is formed on the hand to be attached/detached.
In this prior art, the outward tapered surface is pressed downward to bring its cylindrical outer circumferential surface into contact with the locking ball, thereby causing the locking ball to project radially outwardly. The projecting locking ball is engaged with the inward tapered surface, thereby coupling the hand to the attaching/detaching mechanism. The cylindrical outer circumferential surface is pulled upward and is set so that the outward tapered surface is located aside the locking ball to permit a radial movement of the locking ball. Thus, an engagement between the inward tapered surface and the locking ball is released, and the hand can be detached from the attaching/detaching mechanism. As a result, in the conventional hand attaching/detaching device, when the hand is exchanged, an axial moving distance can be shortened, and a time required for an exchanging operation can also be shortened.
As described above, the hand attaching/detaching device is required to have a structure having a connection mechanism for supplying air and power to the hand, and for performing communication, and the like. However, in this connection mechanism, if the numbers of sensors and actuators to be arranged in the hand are to be increased, the number of contacts in an attaching/detaching portion between the hand and the attaching/detaching mechanism is increased. As a result, the weight of the robot arm distal end portion including the hand is undesirably increased, and the output of a motor for driving the robot must be increased.
In this connection mechanism, a disconnection state is always monitored. When the disconnection state is detected, a warning operation is executed as an abnormal state. However, in the hand attaching/detaching device, a hand detached state is similar to the disconnection state, and the disconnection state cannot be distinguished from the hand detached state.
The attaching/detaching mechanism between the robot and the hand requires a printed circuit board constituting an electrical circuit for sending signals to actuators such as motors for driving finger members of the hand, or supplying outputs from encoders for detecting a rotational speed and a rotational position of the motors of the hand to a control circuit in the robot. The conventional printed circuit board has a rectangular shape.
When a rectangular printed circuit board is assembled in the hand attaching/detaching mechanism, the following problems are posed.
That is, as shown in FIG. 20, when a printed circuit board A has a rectangular shape, a packing density of circuit parts mounted on the printed circuit board is undesirably decreased. More specifically, when the printed circuit board A is to be stored in a cylindrical proximal portion B of the hand, the printed circuit board A having a smaller area than a cylindrical storage area in the proximal portion B can only be stored, and a total of four dead spaces C are formed, as shown in FIG. 20. In this manner, it is difficult to increase a packing density on the printed circuit board A. As a result, when circuit parts are mounted on the printed circuit board A at a required packing density, a large number of printed circuit boards are required, resulting in a large and heavy apparatus.